Question 15185: I am having problems graphing inequalitys on a plane. I never know which side to shade. I just don't understand this concept.
Answer by rapaljer(4671)   (Show Source):
You can put this solution on YOUR website! The rule that I use is not the way most people teaching math use, but I like it. Whenever you have an equation with a
POSITIVE coefficient of y > or >= , you must shade ABOVE the line.
POSITIVE coefficient of y < or <= , you must shade BELOW the line.
That's as simple as it gets! Examples:
2x+3y < 6 Shade Below
2x+3y > 6 Shade Above
2x+3y >= 6 Shade Above
2x+3y <= 6 Shade Below
So, what if you have a NEGATIVE COEFFICIENT of Y? Well, if you multiply both sides of an inequality by a negative, this reverses the inequality, and therefore it REVERSES the RULE!!
2x - 3y < 6 same as -2x+3y> -6 Shade Above!!
See if that helps. If you need more, I might be able to send you a section from my book in a word file.
R^2 at SCC
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